who says we have to use corn or even sugarcane. Has anybody read up on cellulose ethanol?

Cellulosic ethanol can be produced from a wide variety of cellulosic biomass feedstocks including agricultural plant wastes (corn stover, cereal straws, sugarcane bagasse), plant wastes from industrial processes (sawdust, paper pulp) and energy crops grown specifically for fuel production, such as switchgrass. Cellulosic biomass is composed of cellulose, hemicellulose and lignin, with smaller amounts of proteins, lipids (fats, waxes and oils) and ash. Roughly, two-thirds of the dry mass of cellulosic materials are present as cellulose and hemicellulose. Lignin makes up the bulk of the remaining dry mass.

As with grains, processing cellulosic biomass aims to extract fermentable sugars from the feedstock. But the sugars in cellulose and hemicellulose are locked in complex carbohydrates called polysaccharides (long chains of monosaccharides or simple sugars). Separating these complex polymeric structures into fermentable sugars is essential to the efficient and economic production of cellulosic ethanol.

Two processing options are employed to produce fermentable sugars from cellulosic biomass. One approach utilizes acid hydrolysis to break down the complex carbohydrates into simple sugars. An alternative method, enzymatic hydrolysis, utilizes pretreatment processes to first reduce the size of the material to make it more accessible to hydrolysis. Once pretreated, enzymes are employed to convert the cellulosic biomass to fermentable sugars. The final step involves microbial fermentation yielding ethanol and carbon dioxide.

Grain based ethanol utilizes fossil fuels to produce heat during the conversion process, generating substantial greenhouse gas emissions. Cellulosic ethanol production substitutes biomass for fossil fuels, changing the emissions calculations, according to Michael Wang of Argonne National Laboratories. Wang has created a "Well to Wheel" (WTW) life cycle analysis model to calculate greenhouse gas emissions produced by fuels in internal combustion engines. Life cycle analyses look at the environmental impact of a product from its inception to the end of its useful life.

"The WTW model for cellulosic ethanol showed greenhouse gas emission reductions of about 80% [over gasoline]," said Wang. "Corn ethanol showed 20 to 30% reductions." Cellulosic ethanol's favorable profile stems from using lignin, a biomass by-product of the conversion operation, to fuel the process. "Lignin is a renewable fuel with no net greenhouse gas emissions," explains Wang. "Greenhouse gases produced by the combustion of biomass are offset by the CO2 absorbed by the biomass as it grows."